Create base::test::ScopedTaskScheduler.

base/test/scoped_task_scheduler.cc

Index: base/test/scoped_task_scheduler.cc
diff --git a/base/test/scoped_task_scheduler.cc b/base/test/scoped_task_scheduler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9dc822c89258ab562cbfeae9b764cac016e4824b
--- /dev/null
+++ b/base/test/scoped_task_scheduler.cc
@@ -0,0 +1,48 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/test/scoped_task_scheduler.h"
+
+#include <vector>
+
+#include "base/bind.h"
+#include "base/task_scheduler/scheduler_worker_pool_params.h"
+#include "base/task_scheduler/task_scheduler.h"
+#include "base/threading/platform_thread.h"
+#include "base/time/time.h"
+
+namespace base {
+namespace test {
+
+namespace {
+
+size_t GetWorkerPoolIndexForTraits(const TaskTraits&) {
+  // All TaskTraits are mapped to the single worker pool.
+  return 0;
+}
+
+}  // namespace
+
+ScopedTaskScheduler::ScopedTaskScheduler() {
+  DCHECK(!TaskScheduler::GetInstance());
+
+  // Create a TaskScheduler with a single thread to make tests deterministic.
+  std::vector<SchedulerWorkerPoolParams> worker_pool_params_vector;
+  worker_pool_params_vector.emplace_back(
+      "Test", ThreadPriority::NORMAL,
+      SchedulerWorkerPoolParams::IORestriction::ALLOWED, 1, TimeDelta::Max());
+  TaskScheduler::CreateAndSetDefaultTaskScheduler(
+      worker_pool_params_vector, Bind(&GetWorkerPoolIndexForTraits));
+  task_scheduler_ = TaskScheduler::GetInstance();
+}
+
+ScopedTaskScheduler::~ScopedTaskScheduler() {
+  DCHECK_EQ(task_scheduler_, TaskScheduler::GetInstance());
+  TaskScheduler::GetInstance()->Shutdown();
+  TaskScheduler::GetInstance()->JoinForTesting();
+  TaskScheduler::SetInstance(nullptr);
+}
+
+}  // namespace test
+}  // namespace base